Skip to main content
ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Research Project #443947

Research Project: Optimizing Production Systems for Removal of Ammonia

Location: Warmwater Aquaculture Research Unit

Project Number: 6066-31000-016-037-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Apr 1, 2023
End Date: Mar 31, 2024

Catfish aquaculture production systems began as large ponds with relatively few fish and over time have transformed to systems with numerous fish in smaller ponds. This increase in production intensity results in ponds that require large amounts of commercial feed to grow the fish. Excess protein from feeding results in the loading of nitrogen in ponds, typically in the form of ammonia, which can be toxic to fishes. The first objective of this project is to determine if the rate and pattern of ammonia accumulation is different in split-pond and intensively aerated production systems. This objective will be accomplished by completing two subobjectives. First, we will measure and compare accumulation of different forms of organic and inorganic nitrogen in four split-ponds and four intensively aerated ponds over two distinct growing seasons in ponds at Stoneville, MS. The second subobjective will utilize nitrogen budgets to quantify gains and losses of nitrogen. The second objective is to characterize the underlying mechanisms that contribute to ammonia accumulation, transformation, and removal in split-pond and intensively aerated production systems. This will be accomplished by working on the following subobjectives. First, we will map the spatial and temporal variability of dissolved oxygen concentration in split-ponds and intensively aerated ponds. Second, we will use in situ and laboratory experiments to measure rates of nitrification and denitrification of soil and water. Finally, we will utilize molecular techniques to characterize microbial populations in split-ponds and intensively aerated ponds.

Split-ponds and intensively aerated ponds will be used to evaluate accumulation and removal rates of ammonia, nitrite, and nitrate to determine if microbial processes differ. Hybrid catfish will be raised at stocking rates consistent with catfish industry practices in four intensively aerated ponds and four split-ponds over two production cycles. After the conclusion of each production cycle, production variables will be recorded and the different forms of inorganic and organic nitrogen will quantified. These water quality measurements will be used to assess whether these two production systems differ in how their nitrogen budgets differ. To characterize how the underlying ecology or mechanics of these two production systems differ, in situ measurements of nitrification and denitrification will be used to quantify rates of ammonia transformations. To complement these data a survey of the distribution of dissolved oxygen will be performed. Dissolved oxygen concentration is a major limiter of nitrification and denitrification and understanding how it changes spatially and temporally will help describe the function of these ponds. Finally, microbial populations will be assessed using metagenomics and other molecular techniques. These assays will describe the underlying microbial communities that are responsible for performing nitrification and denitrification.